Electron-discharge apparatus



2. m m. M. ummsb .mimm s Q e 5, Y t .a M

A W HULL ELECTRON DISCHARGE APPARATUS Filed sept. a, 1921 Patented Dec. e, 1925.

UNITED sra'rlasA PATEnroFFlcE.

ALBERT W. HULL, OF SCHENECTADYrNEW YORK, ASSIGNOR T0 GENERAL ELECTRIC COMPANY, A CORPORATION 0F NEW YORK.

ELECTRON-DISCHARGE APPARATUS.

Application led September 8,11921. Serial No. 499,2/93. i

To all 11i/20m it may concern:

Be it known that I, ALBERT W. HULL, a citizen of the United States, residin at Schenectady, county of Schenectady, tate of New York, have invented certain new and useful In'lprovements in Electron-Discharge A paratus, of which the following is a speci cation.

My present invention relates to electron discharge apparatus and more particularly to the .well-known type of apparatus' in which current is carried across an evacuated space chiefly by means of electrons without any substantial gas ionization effects being produced or influencing the fiow of current.

rihe object of my invention is to provide lan improved apparatus of the type mentioned and method of operating the same .which will possess marked -advantages over apparatus previously employed. ln carrying my invention into effect I employ preferably a threeelectrode device having the usual electron emittingy cathode, anode and controlling Grid enclosed in an evacuated receptacle. The electrodes of this device are preferably arranged in substantially circular s mmetry with respect to one another'. ln a dition I provide means for producing a magnetic field in the space between the electrodes in a direction at' a ri ht angle to the paths of the electrons. is means for producing the magnetic field'may be in the form of a coil surrounding the has already been mentioned may receptacle and this coil may be supplied with current from the output circuit o the device.

The current throughthe device may be controlled by means of the grid electrode to perform any of the functions for which a device of the type mentioned is adapted. When the magnetic field produced is propcrly proportioned the device `may possess several operating advantages over three electrode devices of similar type as previously operated. When such devices are employed as amplifiers the` degree of .amplificat1on which may be obtained depends uponl the slope of the curverepresenting the relation between grid potentialandoutput cur.- rent. By the use of a magnetlc' field control in conjunction with the electrostatic fieldA` control theslo e of this curve nary, overa well define operating range of y rent continues to flow between cathode and anode even when the grid potential becomes negative and the current decreases rather slowly as the negative rid potential is increased to a point at wh How. By the use of a magnetic field in accordance with my invention the current flow may be caused to decrease to substantially zero very quickly even when the grid potential is positive. This ermits of the operation of the device Wit out the usual biaslng potential on the grid and permits of the substantial interru tion of current at desired periods in an e cient manner.

When the three electrodedev'ice is operated'as a detector and the asymmetry of the current curve is utilized to secure the detector action normal operation takes place at a point where there is a marked change in the curvature of the characteristic current curve. The more abrupt -this change in curvature, the more eliicient the operation of the device. The increase in the slope of lized for producing oscillations as it is desirable in this case that current be supplied to the oscillatin circuit only during certain portions of t e cycle.

It 1s well known that the general effect of a magnetic field at a right angle to the path of a moving electron'is to deflect the electron` causing it to move in a spiral path instead of a straight path. The first result, thereich no current will,

fore, of the application of a magnetic field in the manner described 1s to cause more'of the electrons to strike the grid than would be the case in the absence of the magnetic field. rThis 'edect is especially larve in case the grid is made of slats as descriled in my Yco-pending application, Serial No. 472,139,

ined May 24, 1921.

If the potentials v applied to) the elecl trodes ares properly chosen each lelectron which strikes the grid may produce several secondary or impact electrons which will travel to the more positive anode. As a result the current produced in the. output circuit may beseveral times the current which would be produced therein by the primary electrons emitted by the cathode.'

'When the 'device is employed as an amplifier this phenomenon may be utilized to increase the amplification obtained, and when it is used as an oscillator vthe amplitude of the' i oscillations produced may be -greatly infrom the Output circuit.

f. ear ilamentary cathode 1 adapte heated to .incandescence by a battery 2, or .other lsource. of current, va cylindrical vrange cathodeand the electrodes are all enclosed Thenovel features which I believe to be characteristic of my invention are set forth with paaticularity in the appended claims. Myy invention itself, however, willbest be understood by reference to the following description taken in connection `with the accompanying drawing in which Fig. 1 shows dia ammatically the application of my inventlon to an amplifying system; Fig. 2 shows diagrammatically lits application toia system for producing oscillations for `radio transmission, and Figs. 3, 4 and 5 show characteristic operating curves of devices vwith which mymvention is employed. AS indicated in the drawing, I provide an electron discharge device havin a ligto e rid 3 surrounding the cathode, -and a cylindiiical anode 4 surrounding the grid andcathode. The grid, and anode are `preferably arin circular symmetry about the in an evacuated receptacle 5. An input cir-` cuit between cathode and grid includes a coil 6 which in Fig. 1 'forms the secondary of a transformer` to the rimary 7 of which the currents to be amp iied are supplied. An output circuit between cathode and anode includes a source of current 8, anoutput coil 9 and a second ma etizing coil 10 which preferably surroun s the rceptacle 5 andA the major axis of which 1s preferably substantially coincident ywith the axis of symmetry of the electrodes. The coil 10 is shunted by a condenser 11 of large capacity. In Fig. 1 the output coil is i, coupled to a coil 12 which is included in a ,at which cut-off occurs.

Lacasse transmitting purposes. 4Oscillations may be generated in the system by meansof a feed back connection between output and input circuits which comprises coupling coils15, and 16. In case 1t 1s desired to roduce a negative resistance 1n the grid cn'cult and employ this characteristic for the produc tion of oscillations, the feed back connection may be omitted and a condenser 17 may be inserted in the input circuit in shunt to coil 6, the frequency of the oscillations thus produced being determined by 'the tuning of the resonant circuit formed by-coil 6 and condenser 17. In this caseit 1s necessary to first impress a positive charge upon the grid before oscillations will start. l `This may be accomplished by connecting vone terminal of the condenser 17 by the dotted line connection 18 indicated to a point in the battery 8 instead of directly to thecathode.

In Fig. 3 I have shown lcurves representing the relation between grid potential and anode current under different conditions ot operation. Curve A is a typical characteristic4 ofa three-electrode device asv ordinarily operated, and curve B shows a. corre# sponding characteristic when a magnetic field is employed in the manner described. It will be observed from curve B that-the anode current instead of decreasing gradu ally as the grid becomes more ne ative, decreases very rapidly as the grid becomes negative and reaches a substantially zero value at a much lower negative grid potential than in the case Where the magnetic field is absent. The portion of the` curve B between the' points el and e2 is much steeper than any' portion ofI curve Auand therefore a much greater degree of amplification may be obtained with the device over v i this range than when the device isoperated without the ma 'netic lield. .It should also be noted that'at oth points c, and 02 there are much more abrupt changes in the curvature of the characteristic than are found on curve A. Either of these points therefore may be advantageously employed for operating the device as a detector.

The value of the grid potential at which the flow of current will be interrupted dcpends-in any particular device upon the strength of the magnetic field. In general. the stronger the magnetic field the more positiveor less-negative the grid potential In general also the stronger the magnetic field the steeper the 125 slope of the characteristic curve. In Fig. 4 I have indicate-d the characteristic curve in a case where the magnetic field is strong enough to cut oii' the current when there is a fairly high positive potential on die grid.

This ladjustment may be employed advantageously when the device is utilized for pro `ducing oscillations. The curve C in Fig. 4

supplied to the anode only during the in' tervals represented by the shaded portions of curve C. lt will be noted thatwith the arrangement shown and described it is not necessary to employ any grid leak or biasing battery to adjust the normal grid potential but that etiicient operation may be obtained byregulating the strength of the magnetic field to shorten the time in each cycle of the grid potential during which current will e flow instead of producing a similar effect by means of a' grid bias. v ln case the grid oscillations are properly phased with respect to the oscillations of the anode potential this arrangement will result in a greater ettieiency of operation of the system than when current is supplied tothe-anodeduring the greaterpart of the cycle of grid Y potential.

In the curves shown in Figs. 3 and 4, it is assumed that there is not suiiicient secondary @mission produced from thegrid to produce any appreciable eti'ect upon the eurrcnt in the output circuit. The eii'ect 'of large secondary emission troni the grid is indicated inl `ig. 5. In this figure curve A represents as before the characteristic in the absence of a magnetic field 'and curve B represents the characteristic `with a magnetic tield. Curve D shows the relation between grid current and grid potential, this current being negative or in rthe opposite direction to the usual'grid current by reason of the high secondary emission. Curve B indicates the resultant current in the output circuit produced by the primary electrons which reach the anode and the secondary or lmpact electrons from the grid which flow to the anode. By reason of the j high secondary emission the current which may be supplied to the output circuit is much greater than' that which would be supplied by primary emission alone in the absence of a magnetic tield. 'It will be apparent that by reason ot this effect the amplitude of oscillations supplied by the output circuit may be greatly' increased over their amplitude in the absencefof a magnetic field.

In' the operation of three electrode devices'as oscillators, ditiiculty has been experienced from the destruction of tubes by heavy rushes of current duc to accidental short circuiting of the load. Such beautyV "operating currents are probably duet-o a combination -of causes among 'which are .the fact that when the loadis Wholly or partially short 'H 'circuited the anode potential becomes very much higher than normal and causes a great increase' in the current 'through the tube.

This increase of current 1s prevented in the arrangement shown in Fig. 2 by the series magnetic field.I

The characteristic curves illustrated show the etiect of a constant magnetic field and if desired, this constant magneticfield may be y provided by' a separate constant source of I energy. lYhen, however, this device is em,- ployed as an amplifier of alternating current or as an oscillator, it will usually be more convenient to utilize the series coil 10 for producing the magnetic field. The field produced in this way will be substantially constant by -reason of the large capacityl condenser 11 in shunt to coil 10. It mayV also in some cases be desirable to supply aportion of the magnetic iield from a separate source of energy vand the remainder by means of a series coil.

In some cases when the device `is employed as an oscillator it may be desirable tojmake the condenser 1'1 adjustable and tunethe loop circuit 10. 11 to the frequency of the oscillations to be produced.v While in this cut ott in the output current lnay be obtained. In this ease the circuit 10, 11 may constitute theonly oscillating circuit in the system and may constitute the Work circuit f as, for example, by replacing the condenser 11 by the capacity of the antenna.

What I claim as'new and desire to secure with respect to one another, of a circuit between cathode and anode, means for varying the potential ot said grid, and means for producing by current owing in the circuit between cathode and anode a magneticiield in the space between said electrodes,y the' strength of the magnetic field being so adjusted as to greatly increase over a pre'- determined operating range the slope of the curve` showing the relation between 'grid voltage and anode current over its slope in the absence of such magnetic field.

2. The combinationwith an electron discharge device having a cathode, an anode and a controllinggrid, of a circuit between cathode and anode. means for varyng the potential of said grid and means for poducing by current iowing in the circuit between cathode and anode. a magnetic field 1in the space between said electrodes, the strength 4to greatly increase" over a lpredetermined ing the relation between grid voltage and anodecurrent over its slope inI the' absence of such magnetic field.

3. The combination with an electron dis'- lofi' ofthe magnetic ield -being so adjusted" as"""" range the slope of theecurve showcase the tield will be variable an even sharper charge device having a cathode, an anode and a controlling grid interposed between said cathode and anode, said electrodes being arranged in substantially circular symmctrywith respect to one another, of a circuit between cathode and anode, means for varying the potential of said grid, and means for producing a magnetic lield in the s ace between said electrodes, the strength o the magnetic iield being so adjusted as to greatly increase over a predetermined operating range the slope of the curve showing the relation between grid voltage and anode current over its slope in the absence of such magnetic iield.

4. The combination with an electron discharge device having a cathode, an anode and a controlling grid, said electrodes being arranged in substantially circular symmetry with respect to one another of a circuit between cathode and anode, means for varying the potential of said grid and a magnetizing coil surrounding said electrodes which is included in the circuit between cathode and anode, said coil being so proportioned that the magnetic field produced thereby will greatly increase over a given operating range the slope of the curve showing the relation between gridvoltage and anode current over its slope in the absence of such magnetic field.

5. The lcombination with an electron discharge device having a, cathode, an anode and a controlling grid, said electrodes being arranged in substantially circular symmetry with respect to one another, of a circuit between cathode and anode, means for varying the potential of said grid., and a magnetizing coil surrounding said electrodes which is 'included in the circuit between cathode and anode. and the major axis of which' is substantially coincident with thel axis of 'l charge device having a cathode,

and a controlling grid. said electrodes being increases over a symmetry of the electrodes, said coil being so proportioned that themagnetic field produced thereby greatly increases over a given operating range the slope or' the curve showing the relation between grid voltage and anode current over its slope in the absence of such magnetic field.

6. The combination with an electron disan anode,

arranged in substantially circular' symmetry with respect to one another of a circuit bctween cathode and anode, means for varying the potential of said grid, a magnetizing coil surrounding;r saidy electrodes lwhich is in.- cluded in the circuit between cathode and anode, said coil beingso proportioned that the magnetic field producedthereby greatly given operating range the slope of the curve showingithe' relation between grid voltage and anode current over its slope 1n ,the absence of such magneticfield, anda conde erin shunt to said coil.

cathode and anode,

' varying the potential 7. The combination with an electron discharge device having a cathode, an anode, and a controlling grid, said' electrodes being arranged in substantially circular symmetry with respect to one another ofa circuit between cathode and anode, means for varymg the potential of said grid, a magnetizing coil surrounding said electrodes which is included in the circuit between cathode and anode, said coil being so proportioned that the magnetic iield produced t ereby greatly vincreases over a given 'operating range the slope of the curve showing the relation between grid voltage and anode current over its slope in the absence of such ma etlc field, and a condenser in shunt to sai coil, said condenser in combination with said magnetizing coil forming a circuit which is lresonant to the frequency of the variations in grid potential.

8. The combination with an electron discharge device having a cathode, an anode, and a controlling gud, of a circuit between cathode and anode, means for varying the. potential ,of said grid, a magnetizing coil surroundin said electrodes which is in- -cluded in t e circuit between cathode and anode, said coil being so proportioned that the magnetic held produced thereby-greatly increases over a given operating range the Slope of the curve showing the vrelation between grid voltage and anode current over its slope' in the'absence of such magnetic field, and a condenser in shunt to said coil, .said condenser in combination with said magnetizing coil forming a circuit which is resonant to the frequency of the variations in grid potential. p

9. The combination with an electron discharge device having a cathode, and anode, and a controlling grid, said electrodes being arranged in substantially Acircular symmetr e with respect to one, another, of a circuit etween cathode and anode', mea-ns for varyingthe potential of said grid, a magnetizmg coil surrounding said electrodes y is included .in the circuit. between and the major axis of which is substantially coincident with the axis of symmetry of the electrodes, said coilA being so proportioned that the magnetic which field produced thereby greatly increasesl over a given operating range the slope of the curve showin f the relation between .grid voltage and ane current over its slope in the absence of a condenser in shunt to said coil.

l0. The combination with an electron disi a cathode, an anode, l

charge device having and a controlling grid, said electrodes being arran ed in substantially circular symmetr "wit respect to one another of a circuit of said grid, and a magnetizing coilsurrounding said electrodes such magnetic field, and' etween cathode and anode,lmeans for which is supplied with current from the circuit between cathode and anode, said coil bein so proportioned that the magnetic field pro uced thereby great-ly increases over a given operating range the slope of the curve showing the relation between grid voltage and anode current over'its slope in the absence of such magnetic field. l

' 11. The combinat-ion'with an electron discharge device havinga cathode, an anode, and a controlling grld, said electrodes being arranged in substantially circular symmetry with respect to one another, of a circuit between cathode and anode. means for varying the potential of said grid, aV magnetizing coil surrounding -said electrodes which is supplied with current from the circuit between cathode and anode, saidcoil Vbeing so roportioned that the magnetic field produced thereby greatly increases over a iven operating range the slope of the curve s iowing the relation between grid voltage and anode current over its slope in the absence of such magnetic field, and a condenser in shunt t-o said coil.

12. The combination with an electron discharge device having a cathode, an anode and a controlling grid interposed between said cathode and anode, of means for varying the potential of said grid, an output circuit connected between said cathode and said anode and means for producing a ma'gnetic field in the space between said electrodes, said device bein so constructed and the magnetic field pr uced being of such strength that over a predetermined operating range of grid potential the current supplied by said output circuit will, due to the emission of impact electrons from the grid, be greatly increased over its yvalue inthe absence of the magnetic field. i

13. The combination with an electron dis charge device having a cathode, an anode and'a controlling grid, of means for varying the potential of said grid, an output circuit connected between said cathode and said anode and means for producing bythe current flowing in said output circuit a magnetic field in the space between .said electrodes said device being so constructed and the magnetic field produced -being of such strength that over a predetermined operat ing range of grid potential the current supplled by said -output circuit will, due to t e emission of impact electrons from the grid, be greatly increasedover its value in the absence of the magnetic field.

14. The combination with an electron discharge device having a cathode, an anode and a. controlling grid interposed between said cathode and anode, said electrodes being arranged in substantially circular symmetry with respect to one another, of means for varying the potential of said grid, an outpi 1', circuit connected between said cathode and said anode andmeans. for pro-'i ducing a magnetic field in the s ace bewill, due to the emission of impact electrons from the grid, be greatly increased v its value in the absence of the. magnetic 15. The combination with an electron discharge device having a cathode, an anode, and a controlling grid, said electrodes being arranged in substantially circular symmetry with respect to one another, of means for varying the potential of said grid, an output circuit connected between said cathode and said anode and a coil surrounding said electrodes which is included in the output circuit for lproducing a magnetic field in the space `between said electrodes, said device being so constructed and the magnetic f field produced being of suoli strength that over a predetermined operating range of grid potential the current supplied by saidoutput circuit will, due to the emission of impact electrons from the grid, be greatly increasedv over its value in the absence of the magnetic field.

16. The combinationlwith an electron disoperating-range of gridl potential the current supplied by said output circuit will, due to the emission of impact electrons from the grid, be greatly increased .over its value in the absence of the magnetic field.

lll)

lsuch strength that over a predetermined 17. The combination With an electron discharge device having a cathode, an anode and a controlling grid, said electrodes being arranged in substantially circular symmet'ry with respect to one another, of means for varying the potential of said grid, an output circuit connected between said cathode and said anodeand a coil surrounding said electrodes 'whichi is supplied with current from the output circuit for producing a magnetic field inthe space between .said electrodes, said device being so constructed and the ma etic fieldfjproduced being of such strengti that overa predetermined operating range of grid potentiall ,the current supplied by said output circuit and a controlling grid, said electrodes beingl arranged in substantially circular symmetry with respect to one another of means for varying the potential of said grid, an output circuit connected between said cathode and said anode and a coil surrounding said electrodes which is supplied with current from the output circuit for producing a magnetic `field inf the space between said electrodes,

v.said device being so constructed and the magnetic Qiield produced being of such strength that overa .predetermined operating range of grid potential the current supplied by said output circuit will, due to the emission of impact electrons from the grid, be greatly increased over its value in the absence of the magnetic field, and a condenser in shunt to said coil, said condenser in combinationwith vsaid inagnetizing coil forming a circuit which is resonant to the frequency ofthe variations in grid potential.

19. The combination with an electron dis,- charge device having a cathode, an -anode and a controlling grid, of means for varying thepotential of said grid, an output circuit connected between said cathode and Said anode, means for producing a magnetic iield in the space between said electrodes, and means independent of said magnetic field for producing oscillations in said output circuit, said device being so constructed and the magnetic field produced bein of such strength that over a predeterminedgo erating range of grid potentialk the amplitilde of the oscillations supplied by said i output circuit, will, due to the emission of impact electrons from the grid, be greatly increased over their amplitude in the absence of the magnetic field.

20. The combination with an elec-tron discharge device having a cathode, an anode and a controlling grid, of means for varying the potential of said grid, an output circuit connected between said cathode and said anode, means for producing by the cur rent fiowingin said out ut circuita magnetic field in the space etween -said elec- -trodes, and-means independent of said ma netic field for producing oscillations in said output circuit, said device being so constructed and the magnetic iield produced being' of such strength that over apredetermiiied operating range of grid potential the amplitude of the oscillations supplied by said output circuit will, due to the emission of impact electrons from \,the grid, be greatly increased over their amplitude in the ab sence of the magnetic field.

`output circuit, said device being so constructed and the magnetic field produced being of such strength that over a predetermined operating range of grid potential the amplitude of thc oscillations supplied by said output circuit, will, due to the emission of impact electrons from the grid, be greatly increased over their amplitude in the absence of the magnetic field. l

22.- The combination with an electron discharge device having a cathode, an anode and a' controlling rid, said 'electrodes being arranged in sugstantially4 circular symmetry 'with respect to one another, of means for varying the potential'of said grid, an .output circrit connected between said c ath-v ode an;L said anode, a coil surrounding said electrodes which is included in the output circuit for producing a magnetic field in the space between said e' rtrodes and means sop,

independent of said magnetic field for producin oscillations said output circuit, said device being so construe-ed and the magnetic field produced bein g of such strength that over a predetermined operating range of grid potential the amplitude of t ie oscillations supplied by said output circuit will, due to the emission of impact electrons from the grid, be greatly increased over their amplitude in the absence of the magnetic field.l

23. The combination with an electron discharge device having a cathode, an anode and a controlling grid, of means for varying the potential of said grid, an output circuit connected between said cathode and said anode, a 4coil surrounding said electrodes which is included in the output circuit for producing a magnetic field in the space between said electrodes, and means independent ot said magnetic field for producing oscillations in said output circuit, saidfdevice4 bein so constructed and the magnetic field pro uced being of such strength that over a' predetermined operating range of 'grid potential the amplitude of the oscillations su` plied by said output circuit will, due to t e emission of impact electrons `from the rid, be greatly increased over their amplitu e in the absence of the magnetic field, and a condenser in shunt to said coil, said condenser in combination with said magnetizing coil forming a circuit which is resonant to the llO ` field in the space relquency of the variations in grid potentia 241 The combination with an electron discharge device having a cathode, an anode anda controlling grid, said electrodes being arranged in substantially circular symmetry with respect to one another, of means for varying the potential of said grid, an output circuit connected between said cathode and said anode, a coil surrounding said rece,- `tacle which is supplied with current from the output circuit for producing a magnetic betweensaid electrodes, and means independent of said magnetic field for producing oscillations in said output circuit,

, said device being so constructed and the 4 from the grid, be

magnetic field produced bein strength that over a predetermine o erating range of grid` potential the amplitu e of the oscillations supplied by said output circuit will, due to the emission of impact electrons v reatly increased over their am litude in ,t e absence of the mag- -nieticiel 25. The combination -with an electron discharge device having a cathode, an anode `said anode, a coil and a controlling grid, said electrodes being arranged in substantially circular symmetry with respect toL one another, of means for varying the potential of'said grid, an output circuit connected between said cathode and.

surrounding .said electrodes which is included in the outputv circuit foriproducing a magnetic ieldin the space between said electrodes, the major axis l of said coil'being substantially coincident and means independent withfthe axis of symmetry ofthe electrodes, of said magnetic `field for producing oscillations in said output circuit, said device being so constructed and the magnetic field produced being of such strength that over a predetermined operating range of grid potential the amplitude of t ieoscillations supplied by said output circuit will, due to the emission of impact electrons -from the grid, be greatly increased over their amplitude the absence vof the magnetic field.

ode and grid 26. The combination with yan electron dis-- charge device havin a cathode, an anode and a controlling grid of an oscillating cir- 'cuit connected etween said -cathode and said` gri'd, an -output circuit-connected between said cathodeand said anode, and a coil surrounding said electrodes which '1sI supplied with current from -said output circuit, said device being so constructed and the magnetic field 'produced by said coil being of such value that an emission ofim` v pact electrons from said grid will be produced of sufficient' amount to produce a neg ative resistance in the circuit between cath and cause the generation of oscillations in the oscillating circuit.

27. The combination with an electron disof such .ly coincident with said electrodes,

ycharge device having pressing an alternating -said grid, an outputcircuit connected besa-id anode, :and :i

tween said cathode, and coil surrounding said elect redes which 1s supplied with ,current from said output circuit,

said device being so constructed and the magnetic field produced by said coil being of such value that an^emission of impact electrons from said -grid will 'be produce-fl of suflicient amount to produce a negative resistance inthe circuit between cathode and rid and cause thegeneration of oscillations in. the oscillating circuit. f

28. The combination with an electron dis charge device having a cathode, an lanode and a controlling grid, said electrodes being arranged in substantially circular symmetry with respect to one another, of an oscillating circuit connected between said cathode and said grid,y an output circuit connected between said cathode and said anode, and a coil surrounding said electrodes which is supplied With current from said output circuit, they major axis-of said coil being substantialthe axis of symmetry of said device being so eonstructed and the magnetic field produced'by said coil being of such value that an emission of impact electrons from saidA grid will be produced of sufficient amount'to produce a negative resistance in the circuit between cathode and grid and cause the generation of oscillations in the oscillating circuit.

29. The combination with an electron disa cathode, 'an anode and a controlling grid, of a circuit between cathode and anode, means for impressing an alternating potential on said grid and means for producing by'current flowing in the circuitv betweenca 'hode and-anode a magnetic field in the space between said electrodes,the

' stren th of the magnetic field being so ad-y juste as to greatly shorten the time in each cycle of grid potential during which current will flow to the anode.

30. The combination with an electron dischargeV device having -a cathode, an anode and a controlling grid interposed between said cathode and anodesaid electrodes being4 arranged in substantially circular symmetry with respect to ne another, of a circuit lbetween ycathode and anode, means) forv im- (potential onsaid rid, 'and means ifor pro ucing a magnetic eld in the space b. A tween said electrodes, the strength of the'niagnetic field being so adjusted as to greatly shorten the timein each cycle of grid potential during which c urrfent .will flow to the anode. Y'

31. The combination .charge device having a cathode, aiianode vwith respect to one another, of a circuitbetween cathode and anode, means 'for impressing an alternating potential on said grid, and means for producing by current 'fiowing in the circuit between cathode and Y lanode a magnetic field in the space between ing which current will flow to' the anode.

, field in the being so proportioned that the said electrodes, the strength of the magnetic field being so adjusted as to greatly shorten the time inV each cycle of grid potential dur- 32. The combination with an electron discharge device having a cat-liode, an' anode and a controlling grid, said electrodes being arranged in substantially circular symmetry with respect to one another of a circuit betweenv cathode and anode, means for iinpressing an alternating potential on said grid and a magnetizing coil surrounding said electrodes which is included in the circuit between cathode and anode, said coil magnetic field produced thereby will greatly shorten the time in eachv cycle of grid potential during which current will flow to the anode.

33. The combination with an electro-n dis'- charge device having a cathode,'an anode, and a controlling grid, said electrodes being arranged in substantially` circular symmetr With'respect to'one another, ot a circuit etween cathode and anode, means for impressing an alternating potential on said grid, a magnetizing coil surrounding said electrodes which is included in the circuit between cathode and anode, said coil being so proportioned that the magnetic tield pro- 'duced thereby willxgreatly slliorten the time in each cycle oit gridl potential during which current will flow to the anode.

34. The method of operating an electron discharge device having a cathode, an anode and a controlling grid which consists in producing a flow ot electrons between cathode and anode, impressing a variable potential upon the grid and producing. by means of current carried by the `electron stream a megnetic field in the space between the eleccrease over a predetermined operating range the slo e of the curve 'representing the relation etween anode current and grid potential over its slope in th'e absence of such magnetic field.

35. The method of operating an electrondischarge device having a'cathode, an anode and a controlling ducing a flow of and anode, impressing a variable potential upon the grid and producing a magnetic space between the electrodes of itude to greatly increase over grid which consists in pro-x` sufiicient ma a predetermined o erating range the slope lofthe Vcurve repre nting the relation between anode currend grid'potential over i electrons between cathode in the emission of impact electrons from the grid, and thereby increase over a predeteimined operating range of grid potential thev current flowing inv the output circuit over the value of such current in the absence of a magnetic field.

The method of operating an electron discharge device having a cathode, an anode and a controlling grid and an output circuit which consists in producing a flow of electrons between lcathode and anode, iinpressing a variable potential upon the grid, producing bymeans of current carried by the electron stream a magiietiefeld in the space between the electrodes-otl suoli a value and in suoli a direction thal't it will cause an increase in the emission of impact electrons from the grid, and thereby increase over a predetermined operating range of grid potential the current flowing in the output circuit over the value of such current in 'the absence of a inagnetidfield. c 38. The method of operating an electron dischargel device having a cathode, an anode and a controlling grid and an output circuit which consists electrons between cathode and anode, (producing a magnetic field in the space between the electrodes, producing oscillations in the output circuit independently of the action of the magnetic field and controlling the magnetic fieldin such a way that the amplitude of the oscillations produced in the output circuit will be greatly increased over their amplitude iii the absence ot' the niag netic fiel 39.' The method of operating an electron discharge device having a cathode, an anode and a controlling grid and an output circuit which consists in producing a flow of electrons between cathode and anode,` producing a magnetic lield in the space between the electrodes, producing oscillations in thel output circuit independently of the action .of the magnetic field and controlling the magnetic eld in suchA a way as'to produce a in producing a flow of A civ large emission of impact electrons from the grid by reason of which the amplitude of the oscillations produced in the output circuit will be atly increased over theirl amplitude in 51rd absence of the magnetic field.'

40. The method of operating an electronl discharge device having a cathode, an anode and a controlling grid and an outputcir- 4cuit which consists in producing a ow of electrons between cathode and anode, producing a magnetic field in the ace between the electrodes to cause a 'suicient emission of impact electrons from the gri'd tov4 produce a negative 'resistance in a circuit between Ycathode and grid, utilizin this negative resistance to produce oscil ations and thereby vary the potential of the grid and supplying corresponding oscillations of greater amplitude from the output circuit.

41. The. method of operating an electron dischar@ devicey having a cathode, an anode and a controllin gri'd which consists in producing a iiow o electrons between cathode and anode, impressing an alternating potential upm the grid and producing 1n the space tween the electrodes a m etic field of suicient strength to greatly orten the time in each cycle of grid potential during which current will owto t e anode.

42. The method of operating an electron discharge device having a cathode, an ano'de and a controlling grid which consists in producing a ilow of electrons between cathode and anode, impressing an alternating poten- Vtrous between cat circuit 'and tial upgn the grid and prodifcing in the space tween the electrons by means of current carried by the electron stream a ma netic eld of suiicient strength to great y shorten the time in each cycle of rid potential during which current will ow to the anode.

e 43. The method of operating an electron discharge device having a cathode, an anode and a controlling grid and an output-circuit which `consists in roducing a ow of elecode and anode, mpress- A ing an alternating potential upon the grid and producing in the space between the electrodes a magnetic field of suicient strength to cause an increase in the emission 'of 1mpact electronsA from the grid and-thereby increase over a predetermined range of grid potential the current lowin in the output atly shorten t e time in each cycle 'of gn potential during which current will iiow to t e anode.

In witness whereof, I have hereunto set my hand this 7th day of September, 1921.

ALBERT w. HULL. 

